This application is a national stage application corresponding to international application number PCT/GB98/0003 1, filed Jan. 7, 1998.
1. Field of the Invention
The present invention concerns hybrid integrated circuits and finds particular application in the optical fibre field.
2. Background of the Invention
There has been over recent years a substantial increase in the use of fibre optics both for data communication and data manipulation. The advantages afforded by fibre optics are well-known, but in parallel with this expansion there has arisen a particular problem concerning the coupling of optical fibres either to one another or to other components such as waveguides or optoelectronic devices. For example, in order to achieve good coupling efficiency between two monomode optical fibres, or between a monomode fibre and another element, the actual coupling has to be performed with sub-micron accuracy and in a reliable and stable manner. These requirements have meant that the price of providing optical connections between optical fibres and between fibres and other components is extremely high relative to the actual cost of the elements and has accordingly provided a definite brake on the expansion of electro-optical devices and in particular in the manufacture of hybrid electrooptical integrated circuits.
The manufacture of hybrid integrated circuits involves a number of inter-related processes each of which poses problems regarding the interfacing of different types of devices. These devices comprise optical fibres, laser diodes, photodiodes, and waveguides. Also necessary in the production of hybrid integrated circuits are the provision of electrode contact areas, and ways in which the circuits can be connected to the other electronic devices.
There are thus a number of problems to be solved in the manufacture of hybrid optoelectrical circuits. In addition to the accurate location of the various components and in particular that of the fibre optics an important concern is that interconnection between one pair of the various devices which have just been formed on a substrate will not cause problems with regard to the subsequent mounting on or connection to of other devices to other areas, and that a subsequent device mounting step does not damage or weaken a previous step.
In this specification the term xe2x80x9celectrooptical componentxe2x80x9d covers both active components such as laser diodes and photodiodes and passive components such as waveguides. Of course a waveguide can be associated with electrooptical effects which may include the Kerr effect or thermo-optic effect.
In accordance with one aspect of the present invention there is provided a process of manufacturing a hybrid electrooptical device comprising a process for manufacturing hybrid electrooptical chips comprising:
providing a wafer substrate with a plurality of areas each of which in the final chip is to mount at least one electrooptical component;
treating the surface of the wafer photolithographically so as to generate a mask whereby at least one groove can be anisotropically etched in each area of the substrate so that the groove can mount an optical fibre;
forming features for at least one electrooptical component on each of said areas for connection with an optical fibre when the latter is mounted in said groove; and
anisotropically etching the groove in the substrate so that the groove can receive an optical fibre in such a manner that the fibre can be coupled to the electrooptical component.
In accordance with a second aspect of the present invention there is provided a method of mounting an optical fibre in a substrate comprising:
providing the substrate with a protective layer, masking the protective with a first masking layer so that the protective layer can be etched to define a pattern whereby a groove can be anisotropically etched in the substrate, removing the first masking layer;
applying a second masking layer so as to reduce the width of the groove when the latter is anisotropically etched, anisotropically etching the substrate using the second masking layer to form a v-groove in the substrate;
removing the second masking layer, and etching the area of the substrate on either side of the groove to generate recesses on either side of the groove, and mounting an optical fibre in the groove so that the core of the fibre lies above the surface of the protective layer.
In accordance with a third aspect of the present invention there is provided an integrated hybrid chip comprising a substrate, a protective layer on the substrate, a v-groove which has been anisotropically etched in the substrate, and an optical fibre mounted in the substrate and resiliently gripped by portions of the protective layer, the core of the optical fibre lying above the surface of the substrate.